In the hydrometallurgical industry, it is of common practice to refine metal by electrolysis in electrolytic cells especially designed for this purpose. The metals to be refined are usually conventional metals such as copper, zinc, nickel or cadmium, or precious metals such as silver, platinum or gold, and others.
It is also of common practice to use metal plates as anodes or cathodes or both. These metal plates often weight several hundred pounds. Usually, the metal to be refined, or the metal used to carry the electric current, is in the form of plates of a given thickness, which are provided at their upper end with two laterally extending projections, called hanging legs. Such projections facilitate gripping, handling and hanging of the plates on lateral sidewalls of the cells. These projections also serve to electrically contact or insulate the electrode.
In use, the electrode plates which, as mentioned, can each weigh several hundred pounds, are immersed into the cells in parallel relationship and are used as anodes, cathodes or both, depending on the affinity of the metal being refined.
In order to have the electrodes positioned in a precise desired location, it is of common practice to place a component called a “capping board” or a “bus bar insulator” onto the top surface of each lateral sidewall of the cells. These capping boards are used to position the plates with respect to each other. They are also used as electric insulators between adjacent cells and/or the electrodes and/or the ground.
In practice, the capping boards are used not only as supports to position the electrodes, but also as supports to avoid damage to the masonry, concrete or polymer-concrete forming the lateral side walls of the cells during the insertion and removal of the heaving electrodes. They are also used for electrolytic refining and electrowinning of metals. Capping boards are further used in combination with electrically conductive “contact bars”, the purpose of which is to allow electrical connection between the ends of the anodes and cathodes located in adjacent cells. Thus, the combined use of capping boards and contact bars allows both insulation and distribution of electric current.
To achieve proper electrical contact with the contact bar, the plates forming the electrodes are provided with support hanging legs externally projecting on their opposite upper ends. Only one end of the legs of each plate is in contact with a contact bar on one side of the cell where it is located. The other leg of the same plate is held onto the capping board located on the opposite side of the cell in such a way as to be insulated. Thus, the capping board per se plays the role of an insulator and is thus made of insulating material. The contact bar usually extends over the full length of the corresponding capping board in order to connect altogether all the anodes of one cell to all the cathodes of the adjacent cell and vice versa. The contact bar may interconnect all of the cathodes to the anodes on other adjacent cells or perform other electric connection function between electrodes as desired.
In hydrometallurgical refining of metals, there are two main configurations that may be used to support the electrodes: symmetrical configurations using symmetrical anodes and cathodes and asymmetrical configurations using asymmetrical anodes and cathodes. The capping boards and contact bars are provided depending on the type of electrodes to be used. Thus, different capping board and contact bar systems will be used for symmetrical and asymmetrical electrodes.
Additionally, capping boards may be designed to receive one or more contact bars arranged in a parallel relationship. For example, a capping board may be provided with a primary contact bar and a secondary contact which are supplied with two different electric power sources. The primary contact bar may contact anodes and the secondary contact bar may contact cathodes, or vice-versa. Electrolytic cells including three or more contact bars may also be used in electrolytic refinery of metals, such as described in patent documents U.S. Pat. No. 8,308,920, U.S. Pat. No. 6,342,136 and CA 1.201.681.
So far, it has been of common practice to use capping boards made as a one piece structure extending over the full length of the electrolytic cell. Disadvantages and problems with such capping boards may be related to manufacturing and transportation cost, lack of ease during maintenance or replacement, and waste of the whole capping board in case of local wear or damage.
There is indeed a need in the industry for a contact board, capping board and electrode support technology that would overcome at least some of the aforementioned disadvantages and challenges.